Most automotive engines have at least two valves for each cylinder, one intake and one exhaust valve. Since each of these valves operates at different times, separate operating mechanisms must be provided for each valve. Valves are normally held closed by heavy springs and by compression in the combustion chamber. The purpose of any valve-actuating mechanism is to overcome the spring pressure and open the valves at the proper time. The valve-actuating mechanism includes the engine camshaft, the camshaft followers (valve lifters or tappets), pushrods, and rocker arms.
Among the prior art patents that disclose valve operating assemblies and mechanisms are the following: Granz U.S. Pat. No. 1,118,411; Moore U.S. Pat. No. 1,238,175; Reynolds U.S. Pat. No. 1,309,339; Nibbs U.S. Pat. No. 1,684,407; Murray U.S. Pat. No. 2,122,484; Irving U.S. Pat. No. 2,244,706; Bailey U.S. Pat. No. 2,858,818; and Folino 2004/0055552 A1.